Constructing scenarios of regional sea level change using global temperature pathways

The effects of sea level change become increasingly relevant for the Dutch coast. Therefore we construct two scenarios for regional sea-level change in the 21st century. They are designed to follow two temperature pathways, in which global mean temperature rises moderately ('G', +1.5 K in 2085) or more substantially ('W', +3.5 K in 2085). Contributions from all major processes leading to sea level rise are included (ocean expansion, glacier melt, ice-sheet changes, and landwater changes), except glacial isostatic adjustment and surface elevation changes. As input we use data from 42 coupled global climate models that contributed to CMIP5. The approach is consistent with the recent fifth assessment Report of IPCC, but provides an alternative viewpoint based on global temperature changes rather than RCPs. This makes them rather accessible and readily applicable to policy makers and the general public. We find a likely range for the G-scenario of +25–60 cm in 2085, and +45–80 cm for the W-scenario. These numbers have been rounded to 5 cm precision, to emphasise to any end-user of these scenarios that estimated lower and upper limits themselves are uncertain.